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Sometimes I get curious about what's really happening when I play music. Is there really a lot of treble content? The bass sounds really wild in this song, is really special? Am I missing something? Is there substantial content above 10 kHz? What about below 30 Hz? What sounds can my system reproduce?
When I get this itch, I fire up SoundEasy and start its Spectrum Analyser. Then I set the recording mixer to "What You Hear". This routes whatever is playing to the spectrum analyser and I can see the magnitude of the frequencies of what's playing in real time. It's kinda fun for me, and I'm usually surprised by the spectral content of the music.
First off, the system I'm doing this on is my main PC in my study. The satellites are pretty good (see here for details). These are driven by the front L & R channels of a Logitech Z560 4.1 sound system, and I'm still using the Logitech sub woofer, which is a 10" sub with decent response from 30 Hz to about 200 Hz. It looks like the electronics in the Logitech system band-pass the sub across this range, the driver won't respond to a 20 Hz input at all, and its response is attenuated at 25 Hz.
So, what's real bass look & sound like?
Songs with strong audible bass content show a lot of content between 30 Hz and 80 Hz, where kick-bass drums resonate (around 35 Hz) and bass guitars and stringed basses work. There are a few instruments that go a few Hz below 30 Hz. I believe a full sized concert grand goes down to about 27 Hz, and I'm sure there are plenty of acoustic oddities over the years that go a little below 30 Hz. Also, don't forget the few pipe organs in the world with 16 and 8 Hz pipes. That's about it for acoustic and electric stringed bass. Synthizers (and some electronic effects) are another matter. There's really nothing to keep these instruments from making "music" down to 1 Hz, other than the fact that nobody can hear it, and most systems can't reproduce it. Most systhizer music is based on acoustic models with special augmentation that allows attacks and sustains that can't occur in acoustic music.
For lack of a better word, "effects" start at about 25 Hz and run down to dangerously low frequencies (dangerous to your system and your dwelling). Most of us can't discern tones below 25 Hz, and individuals that claim they can tell the difference between 20 Hz and 21 Hz signals (i.e., hear the tone of the sound) are way off the bell curve (if they actually can). These "sounds" are felt, and a strong sub system can really make these tactile sensations come alive and affect how you experience the music.
What's funny/sad is that I can't hear what songs with significant sub-bass content below 30 Hz are trying to convey. My system doesn't reproduce these frequencies. Anyway, here are some screen caps I recently did form a play list on Grooveshark. These are mp3s of songs people like to test their speakers with. If you get interested in using any of these songs, get the CD and use it, or properly ripped FLAC, wave, or high (320 kb/s) bitrate mp3 files for your testing. Some of the songs on the Grooveshark site don't sound right...
This is Bass, I love You by the Basstronics.
The loudest bass beats (some kind of synthesizer) were shaped the same as above, but at 30 Hz or above. The big bass tone shown here was pretty weak on my system. These bass beats would start at 30 or 40 Hz, then roll down about 10 Hz and fade out. The strong hits would start at 40 Hz and sound strong down to 30 Hz. The hits at 30 Hz would start strong, then fizzle out as they rolled down into the low cut filter on my sub.
This is another screen cap from Bass I Love You. The immense sub-bass signal is a rolling note that starts at about 20 Hz and just keeps going lower. I have SoundEasy set to work from 5 Hz to 50 kHz. They way it looked this signal rolls all the way down to DC, it was still going strong when it exited the graph at 5 Hz.
I'm all for art, but if I was using a big sub, a 500 to 1000 watt amp, and no low cut filter when playing this loud enough to experience it (you can't hear this, just feel it) I'd be really pissed if my driver's voice coil melted before the amp's protection circuitry kicked in. You would stand a very real chance of blowing the amp too. This is why low-cut filters are important in big bass and sub-bass systems, and DC coupling is not a good idea on most equipment...
This is Ain't Wastin' Time, by The Allman Brothers. The peak at 100 Hz is a bass guitar, and the lower peak is probably noise generated by the kick-bass. This song sounds like the classic rock it is, natural, un-augmented bass. Since the bass guitar is playing a melodic bass line there's a lot of upper bass content without the low pitched 30 - 60 Hz thump a simple rhythmic bass line gives a song. This makes the song sound a bit bass shy.
This is from Black Friday by Steely Dan, like the Allman Brothers song above it, it's just a bass guitar and kick-bass providing bass. Here the bass guitar is playing a rhythm line and the bass reinforcement for the song is lower than in the Allman Brother's song. It's also very lightly reinforced by a synthesizer.
This is Mombasa, by Hans Zimmer. The giant bass thing keeping the beat hits at 50 Hz throughout the song, but it has big undertones down to 30 Hz or lower. The neatest thing about this song is the outrageous bass melody in the middle of the song. The huge fog-horn/steam-horn sound starts at 40-50Hz and slides down to 30 Hz. They're using overtones from 100 Hz to 1000 Hz that make this happen, but it's still the first time I've heard something like that, it's neat. I think the 12 Hz peak above is noise or an unintended artifact from some effect. It's low level relative to the base line would make it very hard to feel.
I got a little carried away, trying to characterize the sounds I was hearing. My total lack of knowledge about music is glaring, but it was fun to try to describe what was moving me as I listened to these songs.
To those who play, my apologies for my simple-minded nomenclature.
Jay R. Taylor
Dec 30, 2010
This is from Just Like This Train, by Joni Mitchell. The stuff below 10 Hz is noise. The bass in this song pretty much stops at 40 Hz.
This is Into The Void, by Nine Inch Nails. I've seen this before when looking at their music on a spectrum analyzer. The peak at 10 Hz is part of their music, it looks like an effect on the kick-bass. Hits seem to roll off into inaudibility. It's a neat effect, but there's substantial energy below 20 Hz in this song, try not blow anything up.
This is Hallelujah, by Mannheim Steamroller. The bass synthesizer provides bass like nothing natural can. Wild attacks, crazy overtones and sustain in low bass notes that that doesn't decay like it would in mechanical systems (acoustic or electric stringed bass). While there's substantial content in the 25 to 30 Hz region, it's well balanced with a lot of mid and upper bass content, making the big bass notes special when they happen. Also, there is very little fundamental content below 30 Hz, just an occasional blip bouncing around between 20-25-30 Hz, then fading away.
This one will tax bass systems, but shouldn't blow anything up. I'm not sure how you'll know if the synthesizer sounds right though. What's one sound like in its native environment? :-)
This is Godwhacker, by Steely Dan. A more modern bass track than their older stuff. It's a softer sound on the kick-bass, and a louder bass guitar (augmented some other way? it still sounds tight, like all of their music).
Here's Fast Car, by Tracy Chapman. The kick-bass looks like it's augmented a bit, giving a real full, low impact sound, and the bass guitar is playing a low rhythm line. It gives the song a stronger sounding bass line than the old style rock songs above.
This is from Cause We've Ended as lovers by Jeff Beck. Again the classic rock/blues type bass guitar with a kick-bass and no augmentation. You can see the rich harmonics generated by Beck's guitar and an electric piano/synthesizer with lots of vibrato/phasing/panning effects.
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